JPS6265424A - Method for detecting end point of etching - Google Patents

Abstract

PURPOSE:To contrive making the detection of the end point of etching easy by correcting a difference at the n + 1 time by comparing the spectral intensity waveform of the first time with that of the (n) time without making the correction every time while a specimen is being etched. CONSTITUTION:An offset and a gain are adjusted manually at the start, a spectral intensity waveform is monitored and the end point of etching is judged. At the second time, the judgement is carried out under the same conditions of the first time and if the spectral intensity waveform for judging the end point is different from that of the first time, the deviation is computed by a computer 8, the data to a D/A converter 6 for offset and a programable gain amplifier 5 are altered and the spectral intensity waveform is corrected to be made the same with that of the first time. After the correction, the third time judgement is started. Then, the deviation of the third time is fed back for the fourth time, the (n) time is fed back to the n + 1 time and even if the spectral intensity waveform is changed, nearly equal spectral intensity waveform with that of the first time can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an etching end point detection method.

[Background of the invention]

One method for detecting the etching end point of a sample etched using gas plasma by monitoring changes in the spectral intensity waveform is to etch a 1-spectral intensity waveform as described in JP-A No. 59-28340. Monitor from the start until the end point is detected - the amount of offset each time,
A device in which the amount of gain is adjusted is known.

However, in this method, the offset amount and gain amount are adjusted each time one sample is etched, so
This requires higher calculation functions and higher conversion speeds to analog values, which complicates the etching end point detection operation and makes the design more expensive.

[Purpose of the invention]

The purpose of the present invention is to compare the spectral intensity waveform of the first time and the spectral intensity waveform of the IJnth time during etching of one sample, and to correct the difference at the n+1th time, without having to correct each time. By the way.

It is an object of the present invention to provide an etching end point detection method that eliminates the need for arithmetic functions and speeding up conversion to analog values and facilitates etching end point detection operations.

[Summary of the invention]

The present invention provides a method for detecting the etching end point of an etched sample using gas plasma by monitoring changes in the spectral intensity waveform.
Compare the predistributed light intensity waveform with n100 offset and gain WI4 adjustment, and set a digital value so that the n+1th predistributed light intensity waveform matches the first predistributed light intensity waveform based on the difference resulting from the comparison. It is characterized by changing the offset and gain by changing the offset and gain, and compares the 111th spectral intensity waveform with the nth spectral intensity waveform and calculates the difference without making corrections each time during etching of one sample. 95 n + 1 time scale correction.

[Embodiments of the invention]

Emei Figure 1 shows an example of this year's vote. This will be explained with reference to FIG.

FIG. 1 shows the circuit configuration. One spectral intensity waveform is input to the input from the annual offset variable resistor 4 and the digital amount from the computer 8 is converted into an analog value.
The outputs from the A converter 6 are added together, the resulting value is included in the gain amplifier 2I having the variable resistor 3 for annual adjustment, and the output is added to the digital output from the computer 8.
+ Gale is weirder than this.

A/D via programmable gain amplifier 5
Input to converter 7. The digital output value of the A/D conversion "!A7 is taken into the computer 8I, where the computer 8 determines the end point, and outputs the end point determination result, waveform signal, etc. to the output 9.

Next, the control method will be explained using Figure 2. For each start special number, manually adjust the offset and gain, monitor the spectral intensity waveform in that state, and perform the end point determination (manually adjust the gain and offset so that the end point can be determined).

The second time is determined under the same conditions as the first time, and if the spectral intensity waveform for end point determination at that time is different from the first time,
Calculate the deviation with the combination, -Y8, and offset D/
The data to the A converter 6 and the programmable gain amplifier 5 are changed to correct the one-spectrum intensity waveform to be the same as the first one.

After the correction, the third judgment starts. After that, the deviation from the third time is fed back for the fourth time, and then the nth time is fed back to the n+1th time, so that if the spectral intensity waveform changes, it will be almost the same as the first spectral intensity waveform. do.

In this embodiment, the following first-order effects can be obtained.

(1) During etching of one sample, the first spectral intensity waveform can be obtained without making corrections each time! Since the spectral intensity waveform of the Inth time is compared and the difference therebetween is corrected at the (n+1)th time, the etching end point detection operation can be facilitated and the cost of the apparatus can be reduced.

(2) Initially, offset while observing the spectral intensity waveform,
Gain can be adjusted.

(3) Even during etching many times, the monitor input remains almost constant, making it easy to detect the end point.

〔Effect of the invention〕

As described above, the present invention compares the first spectral intensity waveform and @n100 spectral intensity waveform during etching of one sample without making corrections each time, and corrects the difference at the n+1th time. This has the advantage of eliminating the need for arithmetic functions and speeding up the conversion to analog values, and simplifies the end point detection operation.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an example of etching end point detection of 9% according to the present invention, and FIG. 2 is a control method using the apparatus shown in FIG. N1.

Claims (1)

[Claims] 1. In a method of detecting the etching end point of a sample to be etched using gas plasma by monitoring changes in the spectral intensity waveform, the spectral intensity waveform of the first time and the spectral intensity after adjusting the offset and gain of the nth time The method is characterized in that the digital value is changed and the offset and gain are changed so that the (n+1)th spectral intensity waveform matches the first previously distributed light intensity waveform based on the difference resulting from the comparison. Etching end point detection method.